alexem_mex has the right solution! Just go to Users\Library\Preferences\Adobe Fireworks CS5\ and change the permissions on the folder. I just changed the "Everyone" variable to "Read & Write" and Fireworks started up without issue.

I have had same problem on purchased CS5 suite. I noticed that two folders in User/Library/Preferences had a red circle on them with a minus sign. Adobe Fireworks CS5 and Adobe Illustrator CS5 Settings. Time Machine would not let me replace them so I deleted the two folders and recovered them via Time Machine. Red circles disappeared and both programs booted ok. How many times has Time Machine got me out of trouble.

I second this. I tried some of the other suggestions above this post, but they didn't work. I went into the Users/Library/Preferences/Adobe Fireworks CS5 and changed the permissions of the everyone variable from Read Only to Read & Write on the Adobe Fireworks CS5 folder. Once I did this it opened perfectly, just like was mentioned before.